Optical reticle



Jn- 29, 1946 B. sTEcHBART 2,393,832

OPTICAL RETIGLE Filed Aug. 30, 1944 3 Sheets-Sheet 1 BRUNE ETEEHBAHT ATTY.

Jan. k29, 1946; v a STECHBART 2,393,832

OPTICAL RETICLE Filed Aug. 30! 1944 3 Sheets-Sheet 2 INVENTDR iRuNn ETEEHBART EY Mzffgv, AT TY.

Jan. 29, 1946. '3, STEHBART 2,393,832v

OPTICAL RT-ICLE Filed Aug. so, 1944 s sheets-sheet s 2;) 3M V2 fw 4 6, 6f j) 2 i) INVENTUR. BRUNE ETEEHBART EY 7m.

ATT'Y.

Patented Jan. Z9, 1946 OBTICAL RETICLE' Steclibart, Park Ridge; Ill., assigner to. The Belhlillbwellfcompany, Chicago,Y Ill., a Vcorporatiamoflllinnisx:

application Aignsiyso, 1944, serial No. 551,806

mfcreims. (01.. zza-1)y My invention .relates .particularly to optical V.ret-- icles. offthe illuminated type f-romwvhichimages of Ythe.illuminated,'retiele designslthereof-are proiected by. projection objectives `to provide rsig'hting images.

Objects. ci they invention residefin the provisionA of a novelandeiective fopticalv reticlee oi'.Y the abovev type, which provides.- adequate. 'brilliancy throughout the projected image of the `reticle ydesign'thereof,v particularly at the circumferential region thereon, and,k which: provides` adequate sharpness throughoutthaprojected imagei also particularly atfthe circumferential regionthereof.

The invention willebe betterr understood -by reference to. the:accOilflpflllrirlg.r draWingsforming a part hereof andin which?- n Figurer-1, isa. face elevational view-oi an; optical reticle embodyingbnetform Aof my invention;

Fgurea is,l a,sectionalview `on the linel 2-2.of Figure 1 and showingT the, reticle, in cooperative relation with allightfsourcef;

Figure 3 is. apartial face elevational view kof an optical reticle embodying another formotmy invention;

Figure 4 is a sectional view onltheline of Figure 3.and show-ing thefreticleiin cooperative relation with alight source; and:`

Figures, 64 and '7 aretaxialiseetionalviewsof optical reticles. respectively;Y embodying other formscf my inventionandoof which the. reticle of- .Figure '7 is4 shown in cooperative .relation `with a light source.y

Referring. to Figures. v1 Y- and. 2+ ,a -circular Yreticle design. formingamaskof opaquev material; .such as. metal., isdesignated at .iandsis provided-with a. light opening k2.therethrough..at:the reticlei axis 3 and; withan annular.additionallight-opening 4 therethroughdisposed concentricallyof the reticle axis and. consequently .spaced radially'there: from, the opening 4 beinginterruptediby bridging portions 5 connecting thefportionsottheimask inside andrv outsideof the opening:- 4 to provide a unitary mask structure. A

An annular memberaxially engaged at its periphery against. aperipheralv cylindrical flange .'I ofthe mask. I inconcentricfrelation: with themask andthus formswith themaek an yannular: partial: enclosuref lopen,y internally thereof', this` partial enclosure embracingA the. annular light opening 4. The mask I and annularmember 6 are secured in..theaforesaidrelationvby cally of" and? at correspondtnglofc 'extendingfaeute n angles to; the reticlevaxis 3, andh the diametrically smaller reflector 9" isprovided on the'face: cit-the mask I opposedly` related: with the annularmem; ber Ii7 and the diametricallyflargerreif-actor is provided Vonv the facef oi'fithe annularmemher op-y posedly related `with ther-mask;7 thesefreeetors being formedby surfaces of thexnaslcaandran-` nular member asby plating' these.r surf aceswith a highly reflective metal.

TheI smaller or l reticle, :axis adj aeen-tY reflectorY 9 is directedlaway. from`- the mask-1 Land. toward the larger or reticle axis. remote; reflector II.Y to reilectk light, asudesignatedl at.I I,2,.`tovk the larger reector from, as, designated at...i3,` alight source I4, shown as the iilament ofianincandescent lamp yI5,..on and. spaced along the retic1e.a,xisl.3 from `the .mask and reflectors, ,andthe larger re- Ilector is directed toward the smaller reflector and the mask and reflects light, as designated at,I6, soreected thereto through the .annular or reticleiaxis remotelight' opening 4"of"the maskgthus illuminatingl'this light opening., Light also passes along the reticle axis 3 throughv the 'light opening 2 at this axisto illuminatethis opening.'y

By reason of the reflection of theli'ght-through the annular light opening 4 by the reilectcrst 9 and I I, the light passes through this opening in relatively non-dispersive relation with the reticle axis, as compared with light passingthrougli this opening' directly from the light source*v I4, so that the light so reected through this lopening is directed substantially within the covering' angle of a projection objective, not shown', disposed focused relation with theV reticle-y design' forming c mask for the projection of the reticlef design im-` age, with the result that suilicient'li'ghtis` received by the objective from theli'ghtopenlng 4 to provide adequate brilliancy ofthe projected image thereof; it'being obvious that suillcient flight is received by theobjective*froml the light lopening 2 at the reticle axis to provide adequate-prik' lian'cy of 'its' projected" image; Thus, thel proiectedl image' of the entire reticle` design is 'of ade'- quate brilliancy.I

For the purposeof vfurther `increasirigt'he brilliancyV ofthe projected image oftheannular or reticle axis remote' light opening 4;, the reectors 9 and 'I I are concavefin axial planes of the reticle axis'and concentrate the'light at this'lightfopenmg.l

The portions of Atl'refmasls"Irespectii/telyfat the lig-ht, openingsly and. 4-y andl respectively designated aty .|.1 and Y'.I 81 aref spaced, from; eaeh. other longitudnallyV of the reticle axisfandatherportion of the mask at the center light opening 2 is closest to the light source 4, so that the reticle design of the mask is concave in the direction toward the projection Objective with which the reticle is used and thus conforms with the field curvature of the objective with resulting uniformity of sharpness of the projected reticle design image.

While for structural reasons the mask l is comparatively thick at the portion thereof within which lie the light openings 2 and 4 and these light openings are continued to a radial plane of the reticle axis by enlarged light opening portions respectively designated at I9 and 2U, it is obvious that these enlarged light opening portions by reason of their large size do not form the reticle design as do the comparatively restricted openings 2 and 4.

Referring tc Figures 3A 4 and 5, a light transmitting prism of circular disk form and of suitable material, such as optical glassis designated at 2| and is disposed across the reticle axis 22 in concentric relation therewith and the opposite faces 23 and 24 of the prism provide light entry and exit faces. The prism is also provided with two additional faces 25 and 26 providing internally reflecting faces of frusto-conical form and` of different diameters disposed concentrically of and at correspondingly extending acute angles to the reticle axis, and the diametrically smaller refleeting face 25 is provided by an annular depression 21 at the exit face 24 and disposed concentrically of the reticle axis and providing a hub 28 forming the central portion of the exit face. and the diametrically larger reflecting face 26 is formed about the entry face 23, rThe reflecting faces 25 and 26 are preferably silver-coated in the usual manner to increase the reflection therefrom.

The smaller or reticle axis adjacent reflecting face 25 is directed internally of the prism 2| to- Ward the entry face 23 and the larger or reticle axis remote reflecting face 26 to reflect light, as designated at 29, to the larger reflecting face from, as designated at 36, a light source 3|, shown as the filament of an incandescent lamp 32 in Figure 4, on and spaced along the reticle axis 22 from the prism 2| and the reticle design forming mask hereinafter referred to, and the larger reflecting face is directed internally of the prism toward the exit face 24 and the smaller` reflecting face and reflects light, as designated at 33. so reflected thereto toward the exit face.

An opaque reticle design forming mask 34 is Y provided at the exit face 24 and preferably. as

shown, covers the surfaces of the depression 21 and the peripheral portion of the prism including the larger reflecting face 26, thus protectively covering the silver coating of the reflecting faces 25 and 26, the mask preferably being a relatively thick paint coating.

The mask 34 is provided with a first light opening 35 therethrough at the reticle axis and the hub 28 through which light passes along the reticle axis from the light source to illuminate the same, and is provided with an annular second light opening 36 therethrough disposed concentrically of the reticle axis and consequently spaced radially therefrom and disposed in surrounding relation with the depression 21, and through which light opening 36 light is reflected by the larger reflecting face 26 in relatively non-dispersive relation with the reticle axis to illuminate this light opening so that the projected image of this light opening is of adequate brilliancy as hereinbefore explained.

In Figure 4 the portions 31 and 38 of the exif. face 24 of the prism and consequently the corresponding portions of the mask 34, at which the light openings 35 and 36 are respectively disposed, are disposed in the same radial plane of the reticle axis, which results in the reticle design of the mask being flat.

However, in Figure 5 the portions 38 and 40 of the exit face 24 of the prism and consequently the corresponding portions of the mask 34, at which the light openings 35 and 36 are respectively disposed, are spaced from each other longitudinally of the reticle axis and the portion 33 of the exit face and mask at the center light opening 35 is closest to the entry face 23 and the light source 3|, which results in the reticle design of the mask being concave in the direction toward the projection objective with which the reticle is used for the purpose hereinabove explained.

Referring to Figures 6 and 7, a light transmitting prism of circular disk form and of suitable material, such as optical glass, is designated at 42 and is disposed across the reticle axis 43 in concentric relation therewith and the opposite faces 44 and 45 of the prism provide light entry and exit faces. The prism is also provided with three additional faces 46, 41 and 48 providing internally reflecting faces of frusto-conical form and of different diameters disposed concentrically of and at correspondingly extending acute angles to the reticle axis, and the diametrically smallest reflecting face 46 is provided by an annular depression 49 at the exit face 45 and disposed concentrlcally of the reticle axis and providing a hub 50 forming the central portion of the exit face, and the diametrically intermediate and largest reflecting faces 41 and 48 are formed about the entry face 44. The refleeting faces 46, 41 and 48 are preferably silver coated in the usual manner to increase the reflection therefrom.

The smallest or reticle axis adjacent reflecting face 46 is directed internally of the prism 42 toward the entry face 44 and the diametrically intermediate and largest or reticle axis intermediately and farthest remote reflecting faces 41 and 48 to reflect light, as designated respectively at 5| and 52, to the intermediate and largest reflecting faces from, as designated respectively at 53 and 54, a light source 55, shown as the filament of an incandescent lamp 56 in Figure '1, on and spaced along the reticle axis 23 from the prism 42 and the reticle design forming mask hereinafter referred to, and the intermediate and largest reflecting faces are directed internally of the prism toward the exit face 45 and the smallest reflecting face and reflect light, as designated respectively at 51 and 58, so reflected thereto toward the exit face.

An opaque reticle -design forming mask 59 is provided at the exit face 45 and preferably, as shown. covers the surfaces of the depression 49 and the peripheral portion of the prism including the intermediate and largest reflecting faces 41 and 4'8, thus protectively covering the silver coating of the reflecting faces 46, 41 and 48, the mask preferably being a relatively thick paint coating.

The mask 58 is provided with a flrst light opening 60 therethrough at the reticle axis and the hub 50 through which light passes along the reticle axis from the light source to illuminate the same, and is provided with two annular fassa-8e2 raidditicnallightfopenings'i rand-'.8 24 therethrough tot Y diic'rent diameters nand `disposed concentrifeallby g ofl the f reticle Vaxis and vconsequently ad- Jacently and remotely spaced radially -there- @from :and 'disposed in Vsurrounding relation .with 'thefdepression "A9, varidi through-.which light openlings Y1i l :and vft2 light is reflected frespectively by `the intermediate land largest :reflecting ,faces :Il fxmd'l in lrelatively non-dispersive relation .with lathe 'reticleaxisrto il1uminate:these lightopen- 'ings i .so rv:thatsthe f projected imagesY of :these l' light openings l.are of adequate :brilliancy as r4hereinlbeforewexplained.

itacei of thefprism-andconseoluently rthe corl -rrespondingfpm-.tions of the mask 5.59,;,at #which the khlghtpenirigs i60 :and El :rare respectively dispsedgare disposed in'thesameiradial plane-of ztlnezreticle taxis which .results in v,the reticle defsignrofthemask being/fiat.

`zHrmlever, in -Figure `'I vthe portionszGS, Mier-xd ',W'hile 1I :have Athus described Jmy invention, l

do 1notwvisll .to .be limited tothe `precise details described, aexchanges may be :readily Vmade `Without departing from Athe spirit of my invention,

:but having thus described my invention. .I aclairn asrnew and desire` to; securei byiLetters Patent'the following:

vLiln an optical "reticle, :the rcomhination of :a

`reticle y.design forming frnask provided with .an annular light opening `therethrough, and rtwo .generally ufrusto-conical :reflectors of vdifferent diameters disposed,concentrically of said light `opening and Vat correspondingly extending acute yanglestortheir axis and of whichl the diametriv`cally:smaller reflector is directed away from said --mask and towardthe diametrical'ly larger re- 'ector to reflect tothe larger `reflector ligh-t received "fromalong said axis and of which the rlargerlre'flector is directed `toward said smaller yreflector and mask and reects'light so reflected thereto 1 through said lightopening in relatively non-dispersive `relation lwith said 2. In Lan optical reticle, the combination of a circular reticle design forming mask provided with an annular light opening therethrough adjacently spaced radially inward from the periphery of said mask, of an annular member axially engaged against said mask in concentric relation therewith at the peripheries of said mask and annular member and forming with said mask an annular partial enclosure open internally thereof and embracing said light opening, and two generally frusto-conical reflectors of different diameters disposed concentrically of said light opening and at correspondingly extending acute angles to their axis and of which the diametrically smaller reflector is provided on the face of said mask opposedly related with said annular member and is directed away from said mask and toward the diametrically larger reflector to relectcto :the largerlre'tlectorilight receiver from along andfof which .the ilarger'fretlector is provided on the face offsaid--annular--memfber opposedlyfrelated ,withfsaid fmask -andis v"directedtoward said smallerreflectorvand mask and reflects light @so reflected V.thereto `through fsaid light :opening -in relatively nondispersive relationzwith'saidfaxis.

T3. LIn lan optical reticle,thefcombination-of a -reticle design forming :mask provided withv a first Acenter `vlight opening therethrough `and Lwith an annularsecondlight opening therethrough disvposed;'concentrical-ly of said Ilirst llight opening, and ztwo generally frusta-conical r'reflectors `of "diherent .diameters disposed concentrioally yof -saidlight openings yand: at correspondingly extending `acute:anglesftothelrfaxis ando'f which `the fdiametrically smaller re'flexntorr is directed naway from saidinask` tanditoward#the 'diametri- :callyflarger kkre'fdector yto reflect tothe larger relector -v light received Sfrorn along rsaid axis VAand off-which the larger reflector is directed toward said lsmaller Vvreflector and lmask and reflects Llig'htso reflected theretofthrough vsaid second light v opening in'relatively-'non-dspersive relation with lsaid axis, :and therportion yof saidmaskfatsaid Jrst lightopening' being spaced-longitudinally of :said -axis'rom the'portion of-sai'd mask atsaid secondlight opening in rthe-direction opposite )that of said frecelved light.

4. In an optical reticie, -the'combination of. a A-retcle design-'forming mask provided-with Atwo |Y-annular `'concentric light Aopenings therethrough offfdiiferenty diameters,and-y three wgenerallyfrustovconicalreflectors of l'different diametersfdisposed -concentrically of said light openings'and at cor- ;respondinglyiextending'iacute angles to their l-axis vant-'d offwhichl the dlametrically smallest reflector ,ziszdirected away.y from: saidfmaskfand toward 'the 40 d iametrica'lly` intermediate andj largest reflectors vfito reflect litovsaid :intermediate .and 'largest reflectorsilightreceivedfromalong said axis and `of ywhich fsaid intermediate 'and llargest reflectors fiarexdrected toward-said smallest reflector and maskfiand reect lightY sofreflected thereto-respectively through .said `diametrically smaller Hand -larger light openings ink relatively non-dispersive .relation with :said axis.

5.j,In an optical reticle, the Vcombination of "a 50 .'retclefdesl-gn formingy mask provided with a 'first :center light,openingftherethrough `and with two "annular .additional lightfopenings therethrough of Ydifferent diameters .and f disposed concentrically :of said first `=light opening,y and three generally Afrusto-conical ,reiectors of 'different diameters. disposed concentrically of said light openplngsiandwat `correspondingly extending acute Aancgies to'their;r axis .and ofzwhichthe diametrically smallest reflector is directed away from said mask and toward the diametrically intermediate and largest reflectors to reect to said intermediate and largest reflectors light received from along said axis and of which said intermediate and largest reflectors are directed toward said smallest reflector and mask and reflect light so reflected thereto respectively through said diametrically smaller and larger annular light openings in relatively non-dispersive relation with said axis, and the portion of said mask at said diametrlcally smaller annular light opening being spaced longitudinally of said axis from the portion of said mask at said diametrically larger annular light opening and the portion of said mask at said first light opening being spaced longitudinally of said axis from the portion of said mask at said diametrlcally smaller annular light opening both in the direction opposite that of said received light.

6. In an optical reticle, the combination of a light transmitting prism of disk form the opposite faces of which provide light entry and exit faces and said prism having two additional faces providing internally reflecting faces of generally frusto-concal form and of different diameters disposed concentrically and at correspondingly extending acute angles to their axis and of which the diametrically smaller reflecting face is directed internally of said prism toward said entry face and the diametrically larger reflecting face to reflect to said larger reflecting face light received from along said axis and of which the diametrically larger reflecting face is directed internally of said prism toward said exit face and smaller reflecting face and reflects light so reflected thereto toward said exit face in relatively non-dispersive relation with said axis, said smaller reflecting face being provided by a circular depression at said exit face and disposed concentrically of said axis and said larger reflecting face being formed about the periphery of said entry face, and a reticle design forming mask at said exit face and provided with an annular light opening therethrough disposed concentrically of said axis in surrounding relation with said depression and through which light is reflected by said larger reflecting face.

7. In an optical reticle, the combination of a light transmitting prism of disk form the opposite faces of which provide light entry and exit faces and said prism having two additional faces providing internally reflecting faces of generally frusto-conical form and of different diameters disposed concentrically and at correspondingly extending acute angles to their axis and of which the diametrically smaller reflecting face is directed internally of said prism toward said entry face and the diametrically larger reflecting face to reflect to said larger reflecting face light received from along said axis and of which the larger reflecting face is directed internally of said prism toward said exit face and smaller reflecting face and reflects light so reflected thereto toward said exit face in relatively non-dispersive relation with said axis, said smaller reflecting face being provided by an annular depression at said exit face and disposed concentrically of said axis and providing a hub forming the central portion of said exit face and said larger reflecting face being formed about the periphery of said entry face, and a reticle design forming mask at said exit face and provided with a flrst light opening therethrough at said axis and hub and with an annular second light opening therethrough disposed concentrically of said axis in surrounding relation with said depression and through which second light opening light is reflected by said larger reflecting face.

8. In an optical retiole, the combination of a light transmitting prism of disk form the opposite faces of which provide light entry and exit faces and said prism having three additional faces providing internally reflecting faces of generally frusto-conical form and of different diameters disposed concentrically and at correspondingly extending acute angles to their axis and of which the diametrically smallest reflecting face is directed internally of said prism toward said entry face and the diametrically intermediate and largest reflecting faces to reflect to said intermediate and largest reflecting faces light received from along said axis and of which said intermediate and largest reflecting faces are directed internally of said prism toward said exit face and smallest reflecting face and reflect light so reflected thereto toward said exit face in relatively non-dispersive relation with said axis, said smallest reflecting face being provided by an annular depression at said exit face and disposed concentrically of said axis and providing a hub forming the central portion of said exit face and said intermediate and largest reflecting faces being formed about the periphery of said entry face, and a reticle design forming mask at said exit face and provided with a first light opening therethrough at said axis and hub and with two annular additional light openings therethrough of different diameters and disposed concentrically of said axis in surrounding relation with said depression and through which additional annular light openings light is reflected respectively by said intermediate and largest reflecting faces.

9. In an optical reticle, the combination as set forth in claim 7, and further characterized in that the portion of said mask and exit face at said first light opening is spaced longitudinally of said axis from the portion of said mask and exit face at said second light opening in the direction opposite that of said received light.

l0. In an optical reticle, the combination as set forth in claim 8, and further characterized in that the portion of said mask and exit face at said diametrically smaller annular light opening is spaced longitudinally of said axis from the portion of said mask and exit face at said diametrically larger annular light opening and the portion of said mask and exit face at said flrst light opening is spaced longitudinally of said axis from the portion of said mask and exit face at said diametrically smaller annular light opening both in the direction opposite that of said received light.

BRUNO S'IECHBART. 

